Economical control units having a simple construction are known from the related art in particular in the field of motor vehicles. These control units are used for controlling and/or regulating motor vehicle functions, for example the function of an internal combustion engine. These known control units include two integrated circuits, namely a module for a computing device or microcontroller and a peripheral module or peripheral chip. Among other things, a voltage supply, one or more output stages, and interface modules of the control unit are accommodated on the peripheral module.
According to the related art, the computing device and the peripheral module communicate with one another via a so-called microsecond bus (μs-bus). This is a serial bus having approximately 3 to 4 leads. This bus is similar to an SPI (serial peripheral interface) bus. Among other things, a security communication (for example a question and answer communication) between the computing device and the peripheral module takes place via the microsecond bus. Additional leads are also provided between the computing device and the peripheral module, for example for the voltage supply of the computing device.
The computing device of the known control unit also has a so-called UART (universal asynchronous receiver/transmitter) interface via which the serial data are transferred via another lead to the peripheral module from where they are forwarded to means outside of the control unit via the output stage of the peripheral component.
These are, for example, means for implementing the function of the motor vehicle to be controlled or regulated. In particular, such means are, for example, sensors, a diagnostic tester, a vehicle immobilizing system, etc.
A disadvantage of the known control units is the fact that a separate lead for the communication via the UART interface must be provided between the computing device and the peripheral module. This lead must also be connected to a separate pin of the peripheral module, thereby reducing the number of pins available on the peripheral module. However, the number of pins needed on the peripheral module should be kept as low as possible for reasons of cost.